Although born into a Catholic family, Oscar "Zeta" Acosta apparently grew up in a family that was not active in Catholicism. While studying at the University of Southern California on a music scholarship, Acosta was dating an Anglo girl. In order to better be able to provide for her, as they were thining about marriage, Acosta joined the military. He joined the Air Force Band. But not long after that, she split up with him. This was a major trauma in his life. He decided that religion would provide the answers he was looking for. He began attending Catholic church regularly.
Another member of the Air Force band he was in told Acosta about the Baptist, and he started attending a Baptist church near base. He attracted a lot of attention there, as he was quite a rarity: a Hispanic among whites, and a Catholic among Baptists. The young women there were fascinating by him and wanted to hear about his life as a "sinner." Acosta converted and became a Baptist preacher, starting out as a leader of the student or youth group. He was extremely enthusiastic about his new-found faith, and before long he had converted his entire family except his brother.
Acosta served in the military in Panama, where he spent most of his time as a Baptist missionary. He set up and led multiple congregations. He wondered about whether everything was right with him, however, and he made a careful study of the gospels in the New Testament. He kept a list of everything he felt good about while reading about Jesus in the Gospels, and a list of everything he felt bad about. When he was done, the list of things he felt bad about was twenty times larger. He realized he did not believe in Jesus or Christianity. Yet he was the leader of congregations of Panamanians, Indians and American servicemen who looked up to him as a pastor. He still had three months left before his time as a missionary was scheduled to be over, during which time he felt bad about leading congregations and preaching about things he no longer had any belief in. After Acosta finished his time as a Baptist missionary and American serviceman in Panama, he tried unsuccessfully to commit suicide. [Source: Oscar "Zeta" Acosta: The Uncollected Works, edited by Ilan Stavans, Arte Publico Press: Houston, Texas (1996), pages 5-7.]
A particularly important formative relationship for Acosta was his romance with a white Baptist girl named Alice Joy. Acosta dated her in college, and was engaged to her. He spends fifteen pages in his autobiography detailing their time together. But because he was a Catholic and she was a Baptist, this was an "unsurmountable barrier" for them. [Source: Ilan Stavans, Bandido: Oscar "Zeta" Acosta and the Chicano Experience, HarperCollins Publishers: New York (1995), page 31.]
Ironically, after Alice Joy broke up with Acosta, she later married a dark-skinned Italian Catholic. Acosta had learned a great deal about the Baptist faith while dating Alice Joy, and he converted to it not long after she left him. (Stavans, Bandido, page 32)
Acosta became a devout Baptist and a youth leader, and eventually a preacher and missionary in Panama, where he had hundreds of people in multiple congregations who looked to him as their spiritual leader. After about six months of this, however, he felt like he was going crazy. He decided to do a careful study of the Gospels to see if what he was teaching people was really true. He made notes about what he felt good about and what he felt bad about in the New Testament narratives about Jesus. At the end, he found there was twenty times more material that he felt bad about, and he had lost his belief in Jesus. The loss of his Christian faith in Panama was traumatic for him. He continued to preach for three months until his scheduled time was up, although he didn't believe what he was preaching. After all this he attempted suicide, but, as he describes it, he was too cowardly to succeed in the attempt. (Stavans, Bandido, pages 33-34, 42)